W108 M130 Misfire on seemingly random cylinders - Page 2 - Mercedes-Benz Forum

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post #11 of 38 (permalink) Old 05-19-2015, 01:48 PM Thread Starter
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Originally Posted by ctaylor738 View Post
Right now I have two cars with Pertronix and Mercedes wires, and have installed Pertronix in at least a dozen more cars. I haven't seen the problems with arcing. Bosch blue coils work very well with electronic ignition, and the +15 terminal on the coil should get 12V from the ignition, bypassing the ballast resistor(s).

Agree with Will to replace the coil wire. You may have a high resistance wire designed for higher voltage systems. The PN is 130 150 09 18.
I'll definitely replace the wire tomorrow, but I'll have to drive it a short distance (13 km or so) to my local Mercedes dealership. I already had a time booked for it for a brake caliper noise that I haven't been able to source, so I'll just ask the mechanic if he can figure out what's up. The coil lead will be on the desk tomorrow when I drive the car into the shop.

I went out and checked the area around the coil to see what's what. I took some pictures, can some of you tell me if there's anything suspicious to see here?

That lead there seems to have lost a bit of its insulation, but I'm not sure if it's much of an issue. Red wire and connecter are good.


That metallic box was a bit loose, so I tightened the screw a bit. Is that some elaborate system to ground the coil to the chassis? The wire on the right hand side comes from the distributor.


Some cut wires I found and a connector that isn't actually connected to anything. I think these may have been cut or taken off during the electronic ignition installation (was installed before I bought it), but there's 3 wires cut and I can only find 2 ends. Notice the loose connector there too. I moved it away from the chassis so that it won't ground, I guess that's the purpose of it not being stuck to the chassis in some way.
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post #12 of 38 (permalink) Old 05-19-2015, 07:29 PM
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those problems are not hard to figure out , the first thing to do is a scope test of the ignition system , of course , nobody now [ except me ] still use a old fashion scope , this , in a few minutes will diagnose your problem .
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post #13 of 38 (permalink) Old 05-20-2015, 03:03 AM Thread Starter
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those problems are not hard to figure out , the first thing to do is a scope test of the ignition system , of course , nobody now [ except me ] still use a old fashion scope , this , in a few minutes will diagnose your problem .
I've ordered a strobe light, should be here by Thursday. At least I'll figure out if it's timing / spark related.
Anyway, I drove it the short 15 minute trip to my local Mercedes dealership. It drove really, really poorly for the first 5 minutes or so. We're talking absolutely no acceleration in fourth gear and huge misfire. It wouldn't even idle properly, you'd hear it sputter. I drove it very carefully and went a max speed of 30 mph for the first 5 minutes, it seemed like it could hold a speed 'alright' without too much sputtering. The moment it was fully warmed up, I tried taking it up to 45-50 mph and it drove pretty good, not too much sputter. After the 15 minutes or so when I was about to pull into the Mercedes dealership, the misfire was 99% gone, you couldn't even feel it anymore. Just a small RPM lower at idle every few seconds. It still didn't accelerate as good as it used to, I'd say it felt like around half to 2/3 of the power was available.

Now here's the thing. It was a really humid morning that I started it up, and it seems like the air humidity takes much part in the misfire. It'll drive 100% fine when it hasn't rained for days, yet the moment there's some humidity in the air, it'll sputter and misfire greatly. I guess it stopped misfiring because the entire engine bay began to heat up and therefore disperse the humid air / general humidity. Would this sound correct? I'm letting my car in the trusty hands of my mechanic, hoping he will be able to tell me if my theory was correct!
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post #14 of 38 (permalink) Old 05-20-2015, 05:08 AM
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Well, I'd say it's probably not your coil or (if using original transistorized ignition) your switchgear as both of those items can work fine when cold but once they are hot they stop working well. I could be wrong.

Did you replace the distributor cap and rotor?

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post #15 of 38 (permalink) Old 05-20-2015, 06:19 AM
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I'm no expert on fuel injected, but sound like your WUR - warm up regulator. Maybe someone more knowledgeable can verify this.

http://www.justanswer.com/topics-280-se/
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post #16 of 38 (permalink) Old 05-20-2015, 07:21 AM
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Originally Posted by rumb View Post
I'm no expert on fuel injected, but sound like your WUR - warm up regulator. Maybe someone more knowledgeable can verify this.

http://www.justanswer.com/topics-280-se/

That brings up the question that I don't believe has yet been answered. What type of fuel management does the car have? Injection like a 280se? Or dual zeniths like a 280s?

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post #17 of 38 (permalink) Old 05-20-2015, 09:29 AM Thread Starter
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Well, I'd say it's probably not your coil or (if using original transistorized ignition) your switchgear as both of those items can work fine when cold but once they are hot they stop working well. I could be wrong.

Did you replace the distributor cap and rotor?
I replaced the cap and rotor a few days ago to no avail. I also changed all HT leads. It has electronic ignition, so there shouldn't be much of an issue there.

Quote:
Originally Posted by rumb View Post
I'm no expert on fuel injected, but sound like your WUR - warm up regulator. Maybe someone more knowledgeable can verify this.

http://www.justanswer.com/topics-280-se/
The WUR isn't working correctly from the tests I've done (removed filter, no air rushing into it). Probably stuck in the 'hot' position as the car starts up fine and runs alright for around 10 seconds, then begins to idle very poorly and you have to keep it alive with the pedal for another 3-5 minutes. After that, it normally works great.

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That brings up the question that I don't believe has yet been answered. What type of fuel management does the car have? Injection like a 280se? Or dual zeniths like a 280s?
The car is the M130 280 SE with fuel injection. I don't think it has any injection issues, other than the WUR.


Here's the thing though. The old man picked it up from the Mercedes dealership after my mechanic fiddled with it (changed the center lead from the coil to the distributor) and fixed a few other things I haven't had time to. It runs perfectly fine again, just drove it around the block. Has great power and I felt absolutely no misfires. I'm hoping that is the end of it, but as stated previously, it does seem to be rather intermittent (humid air issue?).
I'll take it for a drive tomorrow and report back whether it works or not. For the time being, thanks for the help. Here's a picture of the car in question!
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post #18 of 38 (permalink) Old 05-21-2015, 09:13 AM Thread Starter
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Hi. The misfire returns - and worse!
Drove it a short distance to fill it up, it didn't have much petrol left. I always keep it above a quarter tank, but I guess my frustrations caused me to ignore the fuel gauge. As I got there, the misfire occured fewer times, but still very noticecable and it was very down on power.

So I took an HT lead off with one hand, I kept all my fingers away from the end by holding it at the wire. Then I touched a line coming from the injection pump and I got shocked. Just enough to feel, but definitely an electric shock of some sort. My guess is that the ignition system is grounding itself to the injection pump in some way, or somewhere else leading to the injection pump. How do I fix this and where are the grounds / earth connections on the W108?
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post #19 of 38 (permalink) Old 05-21-2015, 09:58 AM
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You just grounded yourself. You could have touched anything and done the same thing.
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post #20 of 38 (permalink) Old 05-21-2015, 10:01 AM Thread Starter
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You just grounded yourself. You could have touched anything and done the same thing.
I'm honestly not sure if I understand that. Since I'm not touching any part of the spark plug boot, why should I be able to ground myself? I'm not that quick when it comes to the ignition system which makes this issue a real pain to figure out!
The misfire still seems to go away and the car gets up to speed with no issues once it has been at operating temperature for a while. I drove it home yesterday with absolutely no issues. I'm rather sure it gets fuel when it does this trick because it's definitely spraying a lot more out the exhaust than it used to and every time it misfires when it gets to operating temperature, a thud or pop from the exhaust can be heard.

Anyway, going to repost this from up above - it's a picture of the coil seen from up above.

Is the cracked blue wire the ground and would this pose an issue? I'll go press the wire into that boot and then cover it up with some electrical tape to see if there's a difference. If there is, I know which wire to get.


Update: Checked all wires in the ignition system, everything there seems correct, still misfiring and the misfire will be less when hot. It's very intermittent as the car worked beautifully yesterday with not a single misfire after it had been to the Mercedes dealership.

Last edited by Jackpody; 05-21-2015 at 11:37 AM.
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